The real reason they went for Steam on the disc via GOG or Vault is because most of the PC gaming community favors Steam so that would be why. Now I've dealt with dead slow internet connections in the past but they'll do the job eventually even if it takes them a week. As for the refund....that doesn't really apply to KS backers, that's for people who bought the CE from the Larian Vault directly after it was publicly announced a few weeks ago and the reason they can opt for a refund is because the dice were taken out but dice were never part of a KS tier(except the 5k and 10k but nobody got those) plus there's no refunds for KS pledges as per KS policy that Larian has to follow.
OK, I understand... Looks like today "box version" means "steam version" for most of PC gamers
OK, so -logically- no refund, no problem.
I'm a little upset with that Steam problem (to me "no drm on box version" is a lie), but I'm sure Larian did one of the best RPG since... a decade ago, so I'm always looking forward to that Divinity OS !
Thanks everyone for all these explanations !